Data underlying the publication: Mitigating ecosystem impacts of bottom trawl fisheries for North Sea sole Solea solea by replacing mechanical with electrical stimulation
Rijnsdorp, Adriaan ; Depestele, J. ; Eigaard, O.R. ; Hintzen, Niels ; Ivanovic, A. ; Molenaar, Pieke ; O'Neill, F. ; Polet, H. ; Poos, Jan Jaap ; Kooten, Tobias van - \ 2020
Wageningen University & Research
beam trawl - Dutch fleet - habitat - North Sea - pulse trawl
The csv data file “SAR_TBB.csv” contains data on habitat characteristics and fishing effort of the Dutch beam trawl fleet by grid cells of 1 minute longitude * 1 minute latitude in the North Sea used to study the changes in trawling impact on the benthic ecosystem due to the transition from conventional beam trawling to pulse trawling. Habitat variables include %sand, %gravel, %mud, bed shear stress (N.m-2) and level 3 EUNIS habitat type. Fishing effort, expressed as the annual swept area ratio (area swept by the gear in km2 / surface area of the grid cell (km2)), is given for the total Dutch beam trawl fleet and for a subset of vessels holding a pulse license (PLH) when fishing with the conventional beam trawl gear (PLH.T.year) or with the innovative pulse trawl (PLH.P.year).
Solutions for ecosystem-level protection of ocean systems under climate change
Queirós, Ana M. ; Huebert, Klaus B. ; Keyl, Friedemann ; Fernandes, Jose A. ; Stolte, Willem ; Maar, Marie ; Kay, Susan ; Jones, Miranda C. ; Hamon, Katell G. ; Hendriksen, Gerrit ; Vermard, Youen ; Marchal, Paul ; Teal, Lorna R. ; Somerfield, Paul J. ; Austen, Melanie C. ; Barange, Manuel ; Sell, Anne F. ; Allen, Icarus ; Peck, Myron A. - \ 2016
Global Change Biology 22 (2016)12. - ISSN 1354-1013 - p. 3927 - 3936.
climate change - conservation - COP21 - ecosystem model - habitat - marine spatial planning - ocean - ocean acidification - species distribution - warming
The Paris Conference of Parties (COP21) agreement renewed momentum for action against climate change, creating the space for solutions for conservation of the ocean addressing two of its largest threats: climate change and ocean
acidification (CCOA). Recent arguments that ocean policies disregard a mature conservation research field and that protected areas cannot address climate change may be oversimplistic at this time when dynamic solutions for the
management of changing oceans are needed. We propose a novel approach, based on spatial meta-analysis of climate impact models, to improve the positioning of marine protected areas to limit CCOA impacts. We do this by estimating the vulnerability of ocean ecosystems to CCOA in a spatially explicit manner and then co-mapping human activities such as the placement of renewable energy developments and the distribution of marine protected areas. We test this approach in the NE Atlantic considering also how CCOA impacts the base of the food web which supports protected species, an aspect often neglected in conservation studies. We found that, in this case, current regional conservation plans protect areas with low ecosystem-level vulnerability to CCOA, but disregard how species may redistribute to new, suitable and productive habitats. Under current plans, these areas remain open to commercial
extraction and other uses. Here, and worldwide, ocean conservation strategies under CCOA must recognize the longterm importance of these habitat refuges, and studies such as this one are needed to identify them. Protecting these
areas creates adaptive, climate-ready and ecosystem-level policy options for conservation, suitable for changing oceans.
Data from: How much would it cost to monitor farmland biodiversity in Europe?
Geijzendorffer, I.R. ; Targetti, Stefano ; Schneider, Manuel K. ; Brus, D.J. ; Jongman, R.H.G. ; Knotters, M. ; Bogers, M.M.B. ; Staritsky, I.G. - \ 2015
Wageningen University & Research
species richness - farmland biodiversity - habitat - plants - spiders - bees - earth worms - agriculture - agri-environment schemes - biodiversity indicator - common agricultural policy - empirical data - farming system - sampling design - species trend - power analysis
To evaluate progress on political biodiversity objectives, biodiversity monitoring provides information on whether intended results are being achieved. Despite scientific proof that monitoring and evaluation increase the (cost) efficiency of policy measures, cost estimates for monitoring schemes are seldom available, hampering their inclusion in policy programme budgets. Empirical data collected from 12 case studies across Europe were used in a power analysis to estimate the number of farms that would need to be sampled per major farm type to detect changes in species richness over time for four taxa (vascular plants, earthworms, spiders and bees). A sampling design was developed to allocate spatially, across Europe, the farms that should be sampled. Cost estimates are provided for nine monitoring scenarios with differing robustness for detecting temporal changes in species numbers. These cost estimates are compared with the Common Agricultural Policy (CAP) budget (2014–2020) to determine the budget allocation required for the proposed farmland biodiversity monitoring. Results show that the bee indicator requires the highest number of farms to be sampled and the vascular plant indicator the lowest. The costs for the nine farmland biodiversity monitoring scenarios corresponded to 0·01%–0·74% of the total CAP budget and to 0·04%–2·48% of the CAP budget specifically allocated to environmental targets. Synthesis and applications. The results of the cost scenarios demonstrate that, based on the taxa and methods used in this study, a Europe-wide farmland biodiversity monitoring scheme would require a modest share of the Common Agricultural Policy budget. The monitoring scenarios are flexible and can be adapted or complemented with alternate data collection options (e.g. at national scale or voluntary efforts), data mobilization, data integration or modelling efforts.
The influence of a water current on the larval deposition pattern of females of a diverging fire salamander population (Salamandra salamandra)
Krause, E.T. ; Caspers, B.A. - \ 2015
Salamandra : German Journal of Herpetology 51 (2015)2. - ISSN 0036-3375 - p. 156 - 160.
microsatellite loci - genetic-distance - habitat - adaptation - amphibia - success - salmon - home
Fire salamanders are amphibians that exhibit a highly specific reproductive mode termed ovo-viviparity. The eggs develop inside their mothers, and the females give birth to fully developed larvae. The larvae in our study area cluster in two distinct genetic groups that can be linked directly to the habitat (stream or pond) in which the larvae were deposited. Apart from the genetic differences, larvae belonging to the two different habitat types differ in morphological traits, indicating that female fire salamanders already show some type of ecological adaptation to the different habitats. In this study, we investigated whether pregnant fire salamander females of the two habitat-specific genotypes (stream and pond) specifically prefer to deposit larvae in flowing water bodies with a continuous current (i.e., simulating stream habitats) or in water bodies without a permanent water current (i.e., simulating pond habitats). We assumed that the presence of a current is used by the females as a cue to deposit their larvae in the matching aquatic habitat (flowing/standing) according to their own habitat-specific genotype. However, the female fire salamanders of the two habitat-specific genotypes did not show a preference for depositing their larvae in the water body with a water current matching their genotype cluster (stream/pond). Furthermore, the larval genotype did not match the water type in which the larvae were deposited. Overall, this study aimed to test whether fire salamander females of two different habitat-linked genotypes use a water current as a criterion for choosing an aquatic habitat for larval deposition. Our data do not support this hypothesis, leading to the assumption that fire salamander females use other environmental cues to select a water body for larval deposition.
Loss of animal seed dispersal increases extinction risk in a tropical tree species due to pervasive negative density dependence across life stages
Caughlin, T.T. ; Ferguson, J.M. ; Lichstein, J.W. ; Zuidema, P.A. ; Bunyavejchewin, S. ; Levey, D.J. - \ 2015
Proceedings of the Royal Society. B: Biological Sciences 282 (2015)1798. - ISSN 0962-8452 - 9 p.
spatial-patterns - rain-forest - recruitment - consequences - neighborhood - defaunation - habitat - uncertainty - diversity - abundance
Overhunting in tropical forests reduces populations of vertebrate seed dispersers. If reduced seed dispersal has a negative impact on tree population viability, overhunting could lead to altered forest structure and dynamics, including decreased biodiversity. However, empirical data showing decreased animal-dispersed tree abundance in overhunted forests contradict demographic models which predict minimal sensitivity of tree population growth rate to early life stages. One resolution to this discrepancy is that seed dispersal determines spatial aggregation, which could have demographic consequences for all life stages. We tested the impact of dispersal loss on population viability of a tropical tree species, Miliusa horsfieldii, currently dispersed by an intact community of large mammals in a Thai forest. We evaluated the effect of spatial aggregation for all tree life stages, from seeds to adult trees, and constructed simulation models to compare population viability with and without animal-mediated seed dispersal. In simulated populations, disperser loss increased spatial aggregation by fourfold, leading to increased negative density dependence across the life cycle and a 10-fold increase in the probability of extinction. Given that the majority of tree species in tropical forests are animal-dispersed, overhunting will potentially result in forests that are fundamentally different from those existing now.
Positive effect of surrounding rainforest on composition, diversity and late-successional seed dispersal by bats
Vleut, I. ; Levy-Tacher, S.I. ; Galindo-Gonzalez, J. ; Boer, W.F. de - \ 2015
Basic and Applied Ecology 16 (2015)4. - ISSN 1439-1791 - p. 308 - 315.
frugivorous bats - neotropical forest - peruvian amazon - old-growth - birds - size - phyllostomidae - chiroptera - habitat - patches
The configuration of a heterogeneous landscape has an important effect on species composition and landscape processes. The importance of the size, shape and habitat suitability of forest patches has been widely studied, but there is increasing evidence that the spatial context, e.g. adjacency or contact between two landscape elements, can have positive effects on ecological interactions, such as the movement of frugivorous bat species and seed dispersal. We compared the composition, diversity and richness of seed species transported by bats in rainforests and in secondary forests that were either partially or largely surrounded by rainforest, in relation to the fruit species’ life form and successional stage. To capture frugivorous bats we used mist nets with a plastic sheet placed below to allow dropped fruit and seeds from bat feces to be retrieved. Similar species composition and the highest diversity of transported seeds were found in rainforest and secondary forest largely surrounded by rainforest, while the highest number of seed species was recorded in rainforest and secondary forest partially surrounded by rainforest. More bats were captured transporting late successional stage seeds in secondary forest largely surrounded by rainforest. This study demonstrates the importance of rainforest surrounding secondary forests to bat species’ movement and its positive effect on diversity and late successional seed dispersal by bats. Maintaining large areas of rainforest around secondary forests is a useful management strategy for supporting high bat species diversity and abundance, and positively affects the transportation and potential dispersal of seed species of different successional stages.
Is green infrastructure an effective climate adaption strategy for conserving biodiversity? A case study with the great crested newt
Teeffelen, A.J.A. van; Vos, C.C. ; Jochem, R. ; Baveco, J.M. ; Meeuwsen, H. ; Hilbers, J.P. - \ 2015
Landscape Ecology 30 (2015)5. - ISSN 0921-2973 - p. 937 - 954.
population viability analysis - triturus-cristatus - amphibian populations - extinction risk - habitat - conservation - landscapes - management - dynamics - patterns
Context Increasing the amount of green infrastructure, defined as small-scale natural landscape elements, has been named as a climate adaptation measure for biodiversity. While green infrastructure strengthened ecological networks in some studies, it is not known whether this effect also holds under climate change, and how it compares to other landscape adaptation options. Objectives We assessed landscape adaptation options under scenarios of climate change for a dispersal-limited and climate-sensitive species: great crested newt, Triturus cristatus. Methods A spatially-explicit modelling framework was used to simulate newt metapopulation dynamics in a case study area in the Netherlands, under alternative spatial configurations of 500 ha to-be-restored habitat. The framework incorporated weather-related effects on newt recruitment, following current and changing climate conditions. Results Mild climate change resulted in slightly higher metapopulation viability, while more severe climate change (i.e. more frequent mild winters and summer droughts) had detrimental effects on metapopulation viability. The modelling framework revealed interactions between climate and landscape configuration on newt viability. Restoration of ponds and terrestrial habitat may reduce the negative effects of climate change, but only when certain spatial requirements (habitat density, connectivity) as well as abiotic requirements (high ground water level) are met. Conclusions Landscape scenarios where habitat was added in the form of green infrastructure were not able to meet these multiple conditions, as was the case for a scenario that enlarged core areas. The approach allowed a deduction of landscape design rules that incorporated both spatial and abiotic requirements resulting in more effective climate adaptation options.
Trade-offs between pasture production and farmland bird conservation: exploration of options using a dynamic farm model
Sabatier, R. ; Teillard, F. ; Rossing, W.A.H. ; Doyen, L. ; Tichit, M. - \ 2015
Animal 9 (2015)5. - ISSN 1751-7311 - p. 899 - 907.
grassland agroecosystem - viability model - management - biodiversity - heterogeneity - populations - habitat - waders
In European grassland landscapes, grazing and mowing play a key role for the maintenance of high-quality habitats that host important bird populations. As grasslands are also key resources for cattle feeding, there is a need to develop management strategies that achieve the double objective of production and biodiversity conservation. The objective of this study was to use a modelling approach to generate recognisable patterns of bird dynamics in farms composed of different land use proportions, and to compare their production and ecological dimensions. We developed a dynamic model, which linked grassland management to bird population dynamics at the field and farm levels. The model was parameterised for two types of suckling farms corresponding to contrasting levels of grassland intensification and for two bird species of high conservation value. A viability algorithm was used to define and assess viable management strategies for production and ecological performance so as to draw the shape of the relationship between both types of performances for the two types of farms. Our results indicated that, at the farm level, there was a farming system effect with a negative and non-linear relationship linking performance. Improving bird population maintenance was less costly in extensive farms compared with intensive farms. At the field level, the model predicted the timing and intensity of land use, maximising either production or ecological performance. The results suggested that multi-objective grassland management would benefit from public policies that consider levels of organisation higher than the field level, such as the farm or the landscape.
The ecosystem engineer Crassostrea gigas affects tidal flat morphology beyond the boundary of their reef structures
Walles, B. ; Salvador de Paiva, J. ; Prooijen, B. van; Ysebaert, T. ; Smaal, A.C. - \ 2015
Estuaries and coasts 38 (2015)3. - ISSN 1559-2723 - p. 941 - 950.
wadden sea - sediment dynamics - pacific oysters - native mussels - habitat - estuary - stabilization - enhancement - communities - adaptation
Ecosystem engineers that inhabit coastal and estuarine environments, such as reef building oysters, do not only stabilise the sediment within their reefs, but their influence might also extend far outside their reefs, affecting tidal flat morphology and protecting the surrounding soft-sediment environment against erosion. However, quantitative information is largely missing, and the spatially extended ecosystem engineering effects on the surrounding soft-sediment largely unstudied. To quantify this, we measured elevations around eleven natural Crassostrea gigas reefs occurring on tidal flats in the Oosterschelde estuary (the Netherlands). These tidal flats experience strong erosion as a consequence of human interventions in the system. Various reef sizes were chosen to test the proportional effects of reefs on tidal flat morphology. Measurements were used to create 3-dimensional surface maps to obtain properties of the reefs and the surrounding soft-sediment environment. The area of the oyster reefs ranged from 2 to 1,908 m2. Reef length varied between 1 and 61 m, reef width between 1 and 45 m, and reef height between 0.20 and 1.08 m. Reefs varied in shape, going from round shape structures to more elongated ones. We observed elevated areas (>5 cm elevation from the background intertidal slope) on the lee side of all reefs, caused by the interaction between the reef’s structure and locally prevailing wave conditions. The elevated area (i.e. the spatially extended ecosystem engineering effect) affected by the reef was of the same order of magnitude as the reef area. The elevated area was related to reef properties such as reef length, width, and height. Reef length, however, appeared to be the best predictor. These findings contribute to management solutions for coastal adaptation and protection. Our study clearly showed that oyster reefs not only protect the tidal flat under their footprint, but as well an area beyond the boundary of the reef
Directional movement in response to altered flow in six lowland stream Trichoptera
Verdonschot, P.F.M. ; Besse, A.A. ; Dekkers, T.B.M. ; Verdonschot, R.C.M. - \ 2014
Hydrobiologia 740 (2014)1. - ISSN 0018-8158 - p. 219 - 230.
lotic macroinvertebrates - benthic invertebrates - field experiments - upstream movements - river systems - drift - colonization - habitat - refugia - insect
Understanding the trait adaptations associated with mobility in Trichoptera larvae under different flow conditions would enhance the understanding of survival mechanisms under flow stress induced by spates. In stream mesocosms, we mimicked a lowland stream spate by suddenly increasing current velocity above an organic habitat patch from 10 to 30 or 50 cm/s. Subsequently, we investigated whether short-term, small-scale movements in six Trichoptera species were not random but directional and whether the type of movement was related to the magnitude of flow increase. Main types of response distinguished were as follows: (1) resistance, in which the species remained in the habitat patch, (2) upstream or downstream crawling, and (3) being dislodged from the streambed and drift downstream (vulnerability). The type of response observed was related to the species’ ecological preferences and morphological traits. The experiment showed that movement in Trichoptera larvae was directional and flow-dependent. Drift was the main mechanism observed with an increase in current velocity, but upstream crawling and aggregation in the habitat patch were observed as well. The type and magnitude of the response were highly species specific. It appeared that each combination of morphological and behavioral adaptations developed individually for each species under niche-specific conditions.
How many predictors in species distribution models at the landscape scale? Land use versus LiDAR-derived canopy height
Ficetola, G.F. ; Bonardi, A. ; Mücher, C.A. ; Gilissen, N.L.M. ; Padoa-Schioppa, E. - \ 2014
International Journal of Geographical Information Science 28 (2014)8. - ISSN 1365-8816 - p. 1723 - 1739.
mapping forest structure - airborne lidar - habitat - vegetation - availability - environments - biodiversity - probability - explanation - localities
At the local spatial scale, land-use variables are often employed as predictors for ecological niche models (ENMs). Remote sensing can provide additional synoptic information describing vegetation structure in detail. However, there is limited knowledge on which environmental variables and how many of them should be used to calibrate ENMs. We used an information-theoretic approach to compare the performance of ENMs using different sets of predictors: (1) a full set of land-cover variables (seven, obtained from the LGN6 Dutch National Land Use Database); (2) a reduced set of land-cover variables (three); (3) remotely sensed laser data optimized to measure vegetation structure and canopy height (LiDAR, light detection and ranging); and (4) combinations of land cover and LiDAR. ENMs were built for a set of bird species in the Veluwe Natura 2000 site (the Netherlands); for each species, 26–214 records were available from standardized monitoring. Models were built using MaxEnt, and the best performing models were identified using the Akaike’s information criterion corrected for small sample size (AICc). For 78% of the bird species analysed, LiDAR data were included in the best AICc model. The model including LiDAR only was the best performing one in most cases, followed by the model including a reduced set of land-use variables. Models including many land-use variables tended to have limited support. The number of variables included in the best model increased for species with more presence records. For all species with 33 records or less, the best model included LiDAR only. Models with many land-use variables were only selected for species with >150 records. Test area under the curve (AUC) scores ranged between 0.72 and 0.92. Remote sensing data can thus provide regional information useful for modelling at the local and landscape scale, particularly when presence records are limited. ENMs can be optimized through the selection of the number and identity of environmental predictors. Few variables can be sufficient if presence records are limited in number. Synoptic remote sensing data provide a good measure of vegetation structure and may allow a better representation of the available habitat, being extremely useful in this case. Conversely, a larger number of predictors, including land-use variables, can be useful if a large number of presence records are available.
The effectiveness of ditch banks as dispersal corridor for plants in agricultural landscapes depends on species' dispersal traits
Dijk, W.F.A. van; Ruijven, J. van; Berendse, F. ; Snoo, G.R. de - \ 2014
Biological Conservation 171 (2014). - ISSN 0006-3207 - p. 91 - 98.
agri-environment schemes - european countries - biodiversity - grassland - farmland - habitat - colonization - fragmentation - connectivity - pollinators
The effectiveness of agri-environment schemes (AES) in enhancing biodiversity in agricultural landscapes is still strongly debated. In the Netherlands, one of the most widely implemented AES is the management of ditch banks to enhance plant species diversity. Previous research has shown that this type of AES has not led to increases in plant diversity. However, this work also showed that the success of this type of AES may depend on the presence of source populations in the surrounding areas. In this study we investigated if species-rich nature reserves can act as seed sources for agricultural ditch banks under AES and whether this function of nature reserves differs among plant species with different dispersal capacities. We used data collected by farmers over a 10 year period to analyse trends in species richness of target plants and in different dispersal groups in ditch banks under AES at different distances from nature reserves. Our results demonstrate that nature reserves can act as species rich sources in agricultural landscapes and that adjacent AES ditch banks can facilitate the colonisation of the surrounding agricultural landscape. However, the suitability of ditch banks as corridors depends on the dispersal capacity of a species. Particularly water-dispersed species clearly spread from nature reserves into the surrounding agricultural landscape along ditches. In contrast, species without adaptations to disperse over long distances do not show these spatiotemporal patterns.
A Unimodal Species Response Model Relating Traits to Environment with Application to Phytoplankton Communities.
Jamil, T. ; Kruk, C. ; Braak, C.J.F. ter - \ 2014
PLoS ONE 9 (2014)5. - ISSN 1932-6203 - 14 p.
bayesian variable selection - climate-change - ecology - lake - variability - strategies - diversity - habitat - classification - regression
In this paper we attempt to explain observed niche differences among species (i.e. differences in their distribution along environmental gradients) by differences in trait values (e.g. volume) in phytoplankton communities. For this, we propose the trait-modulated Gaussian logistic model in which the niche parameters (optimum, tolerance and maximum) are made linearly dependent on species traits. The model is fitted to data in the Bayesian framework using OpenBUGS (Bayesian inference Using Gibbs Sampling) to identify according to which environmental variables there is niche differentiation among species and traits. We illustrate the method with phytoplankton community data of 203 lakes located within four climate zones and associated measurements on 11 environmental variables and six morphological species traits of 60 species. Temperature and chlorophyll-a (with opposite signs) described well the niche structure of all species. Results showed that about 25% of the variance in the niche centres with respect to chlorophyll-a were accounted for by traits, whereas niche width and maximum could not be predicted by traits. Volume, mucilage, flagella and siliceous exoskeleton are found to be the most important traits to explain the niche centres. Species were clustered in two groups with different niches structures, group 1 high temperature-low chlorophyll-a species and group 2 low temperature-high chlorophyll-a species. Compared to group 2, species in group 1 had larger volume but lower surface area, had more often flagella but neither mucilage nor siliceous exoskeleton. These results might help in understanding the effect of environmental changes on phytoplankton community. The proposed method, therefore, can also apply to other aquatic or terrestrial communities for which individual traits and environmental conditioning factors are available.
Systematic planning and cultivation of agricultural fields using a geo-spatial arable field optimization service: Opportunities and obstacles
Bruin, S. de; Lerink, P. ; Riviere, I.J. la; Vanmeulebrouk, B. - \ 2014
Biosystems Engineering 120 (2014). - ISSN 1537-5110 - p. 15 - 24.
margins - biodiversity - landscape - farmland - machines - guidance - coverage - habitat
This paper describes a geo-spatial arable field optimization service (GAOS) and an assessment of users' experiences after three years of experimental operation. The service was developed in close cooperation with farmers. It allows farmers to optimize the locations of tracks within their fields, explore different options and download these to commercial Global Navigation Satellite System-guided steering systems. GAOS runs as a web service using standards defined by the Open Geospatial Consortium and is being operated by a group of farmers who received a few hours of training. The objective of optimization is to maximize efficiency by avoiding both inefficient turns and discontinuous swaths. Where applicable, released space is converted into field margins that meet environmental objectives and potentially generate additional income. The system provides dedicated functionality for geometrical operations, such as uploading and splitting of fields, merging and splitting of field edges, and manual editing of reference lines in the headlands. Acknowledged beneficial features include reduced expenditures on time and wasted resources and support for planning spraying paths. Given its complexity, most farmers preferred specialists to operate the system rather than operating it themselves. Future development should aim for simpler operation and full support for interactive coverage planning as well as computational optimization.
Group size and dispersal ploys: an analysis of commuting behaviour of the pond bat (Myotis dasycneme)
Haarsma, A.J. ; Siepel, H. - \ 2014
Canadian Journal of Zoology 92 (2014)1. - ISSN 0008-4301 - p. 57 - 65.
sonar signal-design - echolocation behavior - prey detection - habitat - summer - flight - water - netherlands - clutter
Like most bat species, the pond bat (Myotis dasycneme (Boie, 1825)) lives in roosts more or less in the centre of their foraging habitat and are considered central-place foragers. Commuting routes, or flyways, between roosts and hunting areas have an essential ecological function for bats. We summarize the results of research performed on the commuting routes of pond bats between 2002 and 2009. We give, among others, a description on how bats disperse, how to recognize a commuting route, and details about the effort needed to make a complete survey of one commuting route. Furthermore, we make a relation between number of animals on the route and size of their respective roost. The results suggest pond bats are not completely reliant on waterways for reaching their foraging habitat; they use directional dispersal, following commuting routes over waterways in combination with shortcuts over land. These results provide information that can be used to better understand how bats use their commuting routes. Also, the knowledge can be applied to survey work.
Vegetation factors influencing density and distribution of wild large herbivores in a southern African savannah
Gandiwa, E. - \ 2014
African Journal of Ecology 52 (2014)3. - ISSN 0141-6707 - p. 274 - 283.
gonarezhou-national-park - distribution patterns - ungulate diversity - semiarid savanna - water sources - zimbabwe - heterogeneity - populations - elephant - habitat
Understanding factors influencing large herbivore densities and distribution in terrestrial ecosystems is a fundamental goal of ecology. This study examined environmental factors influencing the density and distribution of wild large herbivores in Gonarezhou National Park, Zimbabwe. Vegetation and surface water were predicted to have a stronger influence than anthropogenic-related disturbances (livestock grazing, fires, settlements and poaching) on the density and distribution of wild large herbivores. Aerial survey data for seven common wild large herbivores conducted in 2007 and 2009 and environmental data were collected. Only grass cover explained a significant proportion of the variation in large herbivore densities and distribution. Moreover, only two species densities significantly differed across the Gonarezhou, namely impala and zebra. In contrast, buffalo, elephant, giraffe, kudu and nyala densities did not differ significantly across the Gonarezhou. Overall, the findings only partly support the study prediction. The study results suggest the need to further investigate the roles of environmental factors at smaller scales in order to tease out their relative strengths in influencing density and distribution of large herbivores.
Effects of land-use change and rainfall in Sudano-Sahelian West Africa on the diet and nestling growth rates of an avian predator
Buij, R. ; Folkertsma, I. ; Kortekaas, K. ; longh, H.H. De; Komdeur, J. - \ 2013
Ibis 155 (2013)1. - ISSN 0019-1019 - p. 89 - 101.
field energetics - breeding success - protected areas - hatching order - climate-change - foraging mode - national-park - raptors - habitat - savanna
Raptor populations in Sudano-Sahelian West Africa are being severely affected by widespread habitat alteration which depletes prey populations, potentially aggravated by changing rainfall patterns. We studied Grasshopper Buzzards Butastur rufipennis at nests in natural and transformed habitats in the Sudano-Sahelian region of northern Cameroon to assess the effects of habbitat transformation and rainfall on nestling diet and growth.
The role of breeding range, diet, mobility and body size in associations of raptor communities and land-use in a West African savannah
Buij, R. ; Croes, B.M. ; Gort, G. ; Komdeur, J. - \ 2013
Biological Conservation 166 (2013). - ISSN 0006-3207 - p. 231 - 246.
long-term assessment - protected areas - southern-africa - burkina-faso - conservation - habitat - declines - cameroon - biodiversity - population
To provide insight into raptor declines in western Africa, we investigated associations between land-use and raptor distribution patterns in Cameroon. We examined the role of breeding distribution, species’ migratory mobility, diet, body size, and thus area requirements, on 5-km scale patterns of raptor richness and abundance. We recorded 15,661 individuals, comprising 55 species during road surveys, spanning four annual cycles. Results revealed evidence for the importance of National Parks (N.P.’s), natural vegetation, humans, and cotton in shaping raptor assemblages, but responses differed between functional groups and biogeographical zones. Human populations and natural habitat, interacting with zone, were important predictors of Afrotropical raptor richness, and N.P.’s of Palearctic raptor richness. Areas cleared of natural habitat in the Guinea zone had comparatively rich and abundant large, small sedentary and migratory Afrotropical raptor assemblages, but humans limited positive effects. Palearctic raptor abundance peaked at higher levels of human land-use than Afrotropical raptors. Vertebrate-hunting Palearctic raptor richness was positively associated with cropland, while cotton and human land-use in the Inundation zone had a stronger negative impact on insectivorous Palearctic raptors. Richness of large sedentary raptors declined with increasing distance to N.P.’s, contrary to communal scavenger richness, which increased with human populations. Humans, habitat loss and cotton in the Inundation and Sudan zones had similar, negative effects on small sedentary and small migratory Afrotropical raptor assemblages. We conclude that increasing human populations, natural vegetation loss, and expanding cotton will negatively affect the majority of Afrotropical and insectivorous Palearctic raptors, while vertebrate-hunting Palearctic raptors may benefit from cropland expansion.
A Device to Study the Behavioral Responses of Zooplankton to Food Quality and Quantity
Bukovinszky, T. ; Helmsing, N.R. ; Grau, R.A. ; Bakker, E.S. ; Vos, M. ; UIttenhout, H. ; Verschoor, A.M. - \ 2013
Journal of Insect Behavior 26 (2013)4. - ISSN 0892-7553 - p. 453 - 465.
vertical migration - time allocation - daphnia-pulex - fresh-water - habitat - temperature - gradients - selection - culture - algae
In order to explore the behavioral mechanisms underlying aggregation of foragers on local resource patches, it is necessary to manipulate the location, quality and quantity of food patches. This requires careful control over the conditions in the foraging arena, which may be a challenging task in the case of aquatic resource-consumer systems, like that of freshwater zooplankton feeding on suspended algal cells. We present an experimental tool designed to aid behavioral ecologists in exploring the consequences of resource characteristics for zooplankton aggregation behavior and movement decisions under conditions where the boundaries and characteristics (quantity and quality) of food patches can be standardized. The aggregation behavior of Daphnia magna and D. galeata x hyalina was tested in relation to i) the presence or absence of food or ii) food quality, where algae of high or low nutrient (phosphorus) content were offered in distinct patches. Individuals of both Daphnia species chose tubes containing food patches and D. galeata x hyalina also showed a preference towards food patches of high nutrient content. We discuss how the described equipment complements other behavioral approaches providing a useful tool to understand animal foraging decisions in environments with heterogeneous resource distributions.
Recent switch by the Great Blue Heron (Ardea herodias fannini) in the Pacific northwest to associative nesting with Bald Eagles (Haliaeetus leucocephalus) to gain predator protection
Jones, I.M. ; Butler, R.W. ; Ydenberg, R.C. - \ 2013
Canadian Journal of Zoology 91 (2013)7. - ISSN 0008-4301 - p. 489 - 495.
colonies - advantages - habitat - magpies
The Great Blue Heron (Ardea herodias fannini Chapman, 1901) in the Pacific northwest appears to have modified nesting behaviour in response to the strong recent recovery of the Bald Eagle (Haliaeetus leucocephalus (L., 1766)) population. Previously undescribed, herons now often nest in close association with some breeding eagles, even though eagles depredate heron nestlings, are implicated in the recent reproductive decline of herons, and may induce abandonment of heron breeding colonies. We tested the hypothesis that breeding herons gain protection from the territorial behaviour of eagles. Natural observations and simulated incursions showed that nesting eagles actively repel other eagles within at least 250 m around the nest site, thereby establishing a relatively safe place for herons to nest. Surveys showed that 70% of heron nests and 19% of heron colonies were located within 200 m of eagle nests with high reproductive success. These herons had greater reproductive success than those nesting far from eagle nests.